Reface MIDI pin-out

The Yamaha Reface series keyboards have a small DIN-6 connector that carries both MIDI IN and MIDI OUT signals. The keyboards ship with an adapter that converts DIN-6 to two standard 5-pin DIN connectors. Plug in the adapter cable, connect with standard MIDI cables, and you’re good to go.

A few people on the Yamaha Synth site inquired about the Reface MIDI pin-out. Their questions piqued my curiosity leading to a dive into Yamaha service manuals. The results are posted below along with some essential background information about MIDI signaling.

Use this information at your own risk. That goes for anything on my site!

Although I’ve assembled many boards and kits, I make horrible cables. I much prefer to use commercial MIDI adapters and cables. Life is too short to debug and repair shoddy, unreliable cables. Plug and play solutions are the most flexible; you never know when you’ll need a different configuration of female sockets and male plugs. Adapters like the Yamaha Reface adapter are the most flexible, reliable solution although they are product specific.

The Yamaha part number for the Reface MIDI adapter cable (MD6P-DIN) is ZP893500. If you are a USA customer, you can order the cable on-line from Yamaha 24×7. Last I checked, the cable is also available from the on-line retailer Full Compass. I’ve ordered from both Full Compass and Yamaha 24×7 in the past and they both get a thumbs up.

MIDI background information

If you’re going to do anything with MIDI hardware or software, I strongly recommend becoming a member of the MIDI Association. Please take a look at the MIDI circuit reference design:

This is the original electrical specification diagram. It’s good enough to understand MIDI operation. The original circuit has been superceded by version 1.1 which includes important additions for 3.3 Volt operation and reduced radio frequency interference (RFI). Register to become a member and download the new reference circuit.

As the MIDI specification notes, “The MIDI circuit is a 5mA current loop; logical 0 is current ON.” The MIDI sender and the MIDI receiver are optically isolated. The sender (MIDI OUT) controls an LED embedded within the receiver’s opto-isolator (MIDI IN).

The DIN connector on the MIDI OUT side has the following pins:

  • Pin 1: No connection (NC)
  • Pin 2: Ground
  • Pin 3: No connection (NC)
  • Pin 4: Connected to +5V (3.3V) through a current limiting resistor
  • Pin 5: Serial data output (UART TX)

The DIN connector on the MIDI IN side has the following pins:

  • Pin 1: No connection (NC)
  • Pin 2: No connection (NC)
  • Pin 3: No connection (NC)
  • Pin 4: LED anode (+)
  • Pin 5: LED cathode (-)

Pin 2 may optionally be connected to ground through a capacitor. Please see the current MIDI specification for more info. (Become a member!)

The goal is to turn the opto-isolator LED ON and OFF. The LED polarity (direction of current flow) is important. The MIDI sender turns the electrical current ON and OFF, that is, it turns the LED ON and OFF. This action sends a serial stream of bits from the sender to the receiver.

While writing, it occurred to me — the MIDI Association never formally named these signals. Thus, you get my names like “the thingy connected to the anode of the LED.”

Example: PSR-S910

The following diagram is the MIDI IN and MIDI OUT circuit within the Yamaha PSR-S910 arranger workstation. [Click on the image to enlarge.] I went back to this older product because it uses a transistor pair on the MIDI OUT side, just like the Reface series. That should make it easier to match up the MIDI signals with the Reface DIN-6 pins. Recent products employ a logic gate instead of a transistor pair to switch current through the MIDI loop.

Please note that the S950 MIDI signals are exactly what we expect knowing the MIDI reference design. The “extra stuff” suppresses RFI among other things.

Example: Reface CS

The diagram below depicts the Reface CS MIDI interface circuit (with a few edits for brevity and format). The Reface circuit is similar to the S910 circuit.

Here are the MIDI signals at the Reface DIN-6 pins:

  • Pin 1: MIDI IN, Ground via decoupling capacitor
  • Pin 2: MIDI OUT, Ground
  • Pin 3: MIDI IN, LED cathode (-)
  • Pin 4: MIDI OUT, TX serial data
  • Pin 5: MIDI IN, LED anode (+)
  • Pin 6: MIDI OUT, pull-up to 3.3V

Please note the DIN-6 pin numbering, position and connector orientation!

Now, let’s match up the Reface DIN-6 pins to regular MIDI DIN-5 pins. The MIDI IN match ups are:

       MIDI IN      MIDI IN
    Reface DIN-6   MIDI DIN-5      Function
    ------------  ------------   -------------
                     Pin 1       No connection
        Pin 1        Pin 2       Ground via decoupling capacitor
                     Pin 3       No connection
        Pin 5        Pin 4       LED anode (+)
        Pin 3        Pin 5       LED cathode (-)

I put the MIDI DIN-5 pin numbers in ascending order. The MIDI OUT match ups are:

      MIDI OUT      MIDI OUT
    Reface DIN-6   MIDI DIN-5      Function
    ------------  ------------   -------------
                     Pin 1       No connection
        Pin 2        Pin 2       Ground
                     Pin 3       No connection
        Pin 6        Pin 4       Pull-up to 3.3V
        Pin 4        Pin 5       TX serial data

At this point, I suggest grabbing your Reface MIDI adapter cable and tracing the DIN-6 to DIN-5 connections with a continuity checker. This is the best way to come to grips with the real-world connections and signal/pin positions.

Copyright © 2017 Paul J. Drongowski
Reface and PSR-S910 diagrams are Copyright © Yamaha Corporation

Rainy day ramblings

A rainy New England day and the leaves and pine needles are piling up. Can’t do much of anything outdoors today, so off to GC. (Not that I really want to do yard work.)

No real agenda. I’ve been thinking about Yamaha Montage vs. Tyros 5++ vs. Nord Stage 2 ex vs. Electro 5d. That’s all “long term” as I’m having a lot of fun and staying busy with the S950 and MOX.

I really could use a “lap piano” for rehearsals. (A distant relative of “floor melodica?”) My body ached so much last Wednesday before rehearsal that even an eight pound Korg Triton Taktile was too much to schlep. So, I sang with the group, hoping to internalize the melodies of the new music for the week. This isn’t such a bad idea in any case, since it’s good form to sing along in one’s head while playing — improvisationally or not. A good reminder that, yes, hymns actually have words.

So, the issue of mini-keys rises from the grave like Joan Crawford. About one month ago, I sought and found a Yamaha Reface to try again. As it seems for most interesting music tech, one needs to drive a zillion miles or take two or more trains to find and play Reface, Montage, Korg Arp Odyssey and so forth. And thus it was to play a Reface DX. I had a fair chance to plink away and the DX provided a wide range of solid sounds. But, still, no love for the Reface mini-keys. I simply cannot imagine playing a Reface at rehearsals and even remotely enjoying the experience.

Today’s journey was inspired by a favorable review of the new Korg MicroKorg S in Sound On Sound magazine. What a pretty picture it is; Korg’s industrial design may ape Arturia, but they took the best! The review mentioned the larger mini-keys (what an oxymoron!) of the Microkorg XL+ and I decided to find a comparably equipped Korg.

Happily, today’s trial was the Minilogue, which proved to be a fun time indeed. It’s got a pretty sweet sound for an inexpensive polyphonic analog synth. With the right programming, I could even warp the Minilogue into a “lap piano” good enough for rehearsals. A built-in speaker a la the new Microkorg S would be nice. However, I could easily run it into the JBL Charge 2 that serves as the battery-powered amplifier for the Triton Taktile 49 (my usual rehearsal ax). It’s a shame that the Minilogue isn’t battery powered, too, as it would make a terrific portable instrument.

The Minilogue’s oscilloscope is a real treat and is totally entertaining. It’s also a reminder that I need to add a mini-/micro-oscilloscope to the dining room lab one of these days. The oscilloscope display is a small OLED screen much like the screen in the Triton Taktile.

The Minilogue’s keys are far more playable than the Reface. The keys are longer than typical mini-keys and the black keys (sharps and flats) are narrow. This combination makes for a surprisingly effective keyboard design. I wouldn’t want to play a gig with these, but they are suitable for plinking out melodies and such at rehearsal. (See this article at Synthtopia for a good analysis of the Minilogue’s key size.) Several other Korgs have the same key design: the Korg Arp Odyssey and the “Natural Touch” microKEY, to name two.

I’ll say this for Korg. They may miss the mark sometimes, but these folks are actively innovating at a fast pace!

After messing with the Minilogue, I revisited the Nord Stage 2 ex. This is a fine instrument and is in the same premium range as the Yamaha Montage. Having also revisited the Montage in recent weeks, the Nord’s string and woodwind voices just don’t come up to the same level as Montage. The Montage voices live and breath. Although the Nord is quite good, these voices sound like “sample playback.” Kudos to Yamaha.

I will have more to say about Montage in a forthcoming post. In short, is it time to spring for Montage or wait for the successor to the Tyros 5 (“Tyros++”)?

Time for a cuppa…

Inside Reface DX and Reface CS

With so much to do and learn, it’s been a long while since I’ve taken a peek below the hood of an electronic musical instrument.

Yamaha caught the world by surprise with its Reface series of portable keyboards. So far, there are four models in the series: Reface YC (organ), Reface CP (electric piano), Reface CS (analog modeling synthesizer), and Reface DX (4-op FM synthesizer).

Before I get to the DX and CS, here’s a few thoughts about the YC and CP. According to Yamaha specifications, the Reface YC tone generation engine is “AWM (Organ Flutes)”. This suggests to me that the YC uses a standard AWM tone generation integrated circuit (IC) like the SWP70. Hammond-like “Organ Flutes” have been part of the mid- and upper-tier arranger workstations like Tyros for a very long time. Thus, I suspect that the YC implementation is an updated implementation of the arranger technology.

The Reface CP tone generation engine is specified as “SCM + AWM2”. SCM or “Spectral Component Modeling” is the modeling technique first employed in the flagship CP-1 stage piano. SCM and AWM2 are also used in the CP-4 and CP-40 models. The CP-1 uses three tried-and-true SWP51L tone generation ICs: master, slave and effects. The master and slave generate the base piano tones and the two ICs share the same WAVE ROM. Total WAVE ROM size is 1024Mbits or 128MBytes (organized as 16-bit words) which is a ridiculously small amount of memory for a top quality piano. Such is the power of SCM!

The CP-1’s samples are stored in two Lapis Semiconductor MR26V51252R devices (32M by 16-bit words each). The processor is a Yamaha SWX02 (SH-2A CPU core operating at 135.4752MHz). There’s not much to the CP-1 user interface, so a relatively light-weight, low-cost processor is enough for the job. The SWP51Ls handle all of the heavy computation.

Thus, the Reface YC and Reface CP are relatively uninteresting from a technologist’s point of view. The YC and CP use proven technology from other Yamaha products. That leaves the Reface CS and Reface DX.

Although the CS and DX implement two different tone generation techniques — analog physical modeling vs. frequency modulation (FM) — they are fraternal twins at the hardware level. They share much of the same base hardware design with a few variations to handle their unique user interface requirements.

The CS and DX both use a Fujitsu MB9AF141LAPMC1 processor to handle key and panel scanning. Here’s a quick summary of its characteristics:

    CPU                 Cortex-M3
    CPU Frequency       40MHz

    On-chip flash memory   Main area   64KBytes
    On-chip flash memory   Work area   32KBytes
    On-chip SRAM           SRAM0        8KBytes
    On-chip SRAM           SRAM1        8KBytes

    Peripheral interfaces:
        DMAC            8 channel
        Serial I/F      8 channel
        Base timer      8 channel
        Dual timer      1
        Realtime clock  1
        Watch counter   1
        12-bit A/D      12 channel

This processor is a good choice for embedded control applications where low power and low cost are important. To my knowledge, this is the first product line using an ARM embedded microcontroller.

The Reface CS and Reface DX both use the proprietary Yamaha SSP2 (uPD800500F1-011-KN9-A) for tone generation. The SSP2 is Yamaha’s designated hitter for DSP tasks and is incorporated into many products. The SSP2 has an SH-2A CPU core operating at an internal clock speed of 135.4752MHz. The SSP2 has its own ADC, GPIO, UART, USB and serial audio interfaces. The SSP2 UART handles 5-pin MIDI communications. The SSP2 USB interface handles external USB communications.

The SSP2 has two memory interfaces:

  • DSP RAM: Connecting to 8MBytes of DSP SDRAM.
  • CPU bus: Connecting to 8MBytes of program ROM and 16MBytes of SDRAM.

Memory sizes and devices are the same in both products.

The AUX IN and audio out hardware design is also the same across the two products:

  • PCM1803ADBR ADC: AUX IN analog-to-digital converstion
  • AK4396: Digital-to-analog conversion for OUTPUT L/R and PHONES OUT
  • YDA176 D-Amp: DAC and amplification for internal speakers

This shouldn’t be any surprise. All of the Reface series products ahare the same external jack, power and key switch boards.

Digital audio is transfered serially between the SSP2, the ADC, the DAC and the digital amplifier. The SSP2 generates the master clock (MCLK) and bit clock (BCLK) to synchronize data transfers. MCLK and BCLK are derived from the SSP2 clock, in case you’re wondering about those odd-looking CPU clock frequencies. MCLK is 256*fs and BCLK is 64*fs, where fs is the sampling frequency, 44.1KHz. MCLK operates the AK4396’s digital interpolation filter and delta signal modulator. Data format is I2S and is probably 24-bit as it is in workstation products.

Aside from the other front panel controls, the Reface DX has two major additions: Capacitive sensors for the front panel touch strips and the LCD panel display. The printed circuit board positions for the LCD interface are not populated (i.e., no mount) in the Reface CS as it has no LCD display.

There you have it — two more examples of solid and conservative Yamaha hardware design.

Now, you may find the SSP2 to be incredibly boring. It is, however, a good choice for a low-cost, compact product. The Reface CS and DX need a metal shield over the SSP2, perhaps to control RF emissions, perhaps to radiate heat, or maybe both purposes together. Low power is a vital concern throughout the Reface series due to battery power concerns.

I’m a little hesitant to draw any inferences about future products. The Yamaha Montage supports 128 note, 8 operator FM polyphony. The Reface DX provides a relatively meager 8 note, 4 operator FM polyphony. Thus, there must be considerable hardware resources at work in the Montage. Well-worth the price, one hopes! And speaking of hopes, many people would like an analog modeling extension to the Montage. That would depend, of course, on the availability of spare computational horsepower.

Copyright © 2016 Paul J. Drongowski

(Re)take the stage

A good show starts in the dressing room
And work its way to the stage
— “Get Dressed” by George Clinton

With Winter NAMM 2016 just a few weeks away, I started thinking about how Yamaha might position a new synthesizer workstation (rumored to have the name “Montage”).

Motif has had a long run as a stage instrument favored by many professional touring musicians. It makes a good master controller for a backstage rig and has a wealth of great native sounds. The synth- and piano-key actions are extremely playable with good key-to-sound response.

Over the last few years, Nord and more recently Korg have been taking the stage away from Yamaha. The Nord Stage and Electro series are firmly established as gig boards and the Korg Kronos is coming on strong. Korg products seem to be sprouting everywhere on The Late Night with Stephen Colbert thanks to John Batiste — who can really rock ’em.

I doubt if Yamaha is willing to surrender the stage. This news may disappoint those players who are hoping for a mind-blowing (virtual) analog synthesizer. As a business-person, I would say, “Hmm, we made good money on the stage and in the studio with Motif. Let’s build on that success. Besides, there are plenty of ’boutique’ vendors who make great instruments, like Dave Smith.” Yamaha even granted the name “Sequential” back to Dave Smith.

Yamaha may see the Nord Stage and Korg Kronos as their primary competition for the stage in the synth workstation space. Both instruments combine multiple synthesis techniques into a single integrated package:

  • Wavetable synthesis including sample playback
  • Analog synthesis
  • Frequency Modulation (FM) synthesis
  • Acoustic and electric piano emulation
  • B3 and combo organ emulation

So, which pieces are missing in the current Motif XF? Are you thinking “Reface” yet?

Let’s look at these aspects in turn.

Wavetable synthesis and sample playback

More than a few Internet posters slag AWM (Advanced Wave Memory). I suspect that many of these people would like real analog or modeled analog instead. That’s OK by me because they probably need those sounds for their music. However, there is a wide customer base who need “traditional” instruments (brass, strings, woodwinds, etc.) where sample-playback still rules. AWM is a very successful sample-playback engine and I don’t see Yamaha abandoning AWM.

Yamaha have a new tone generation engine, the SWP70 . The SWP70 is already at work in the PSR-S970 and PSR-S770 arranger workstations . The SWP70 is more than a sample-playback engine as it also performs programmable digital signal processing for effects and more. The S970 implements Motif-quality sounds and effects including Virtual Circuit Modeling (VCM) and the Real Distortion effects that were added to Motif XF in the v1.5 update.

Other posters feel that an SSD is essential for sample streaming. SSD is only one approach, however, and that approach requires a SATA interface for sample I/O. SSD is not necessarily the cheapest design nor does it minimize latency. Yamaha deconstructed the SSD functionality, threw away the SATA interface cost and latency, implemented an Open NAND Flash Interface (ONFI), and embedded sample data caching into the SWP70. The SWP70 has all of the extensibility of NAND flash without the cost of the SATA controller and without SATA bus latency.

As demonstrated by the S970 and S770, the SWP70 is ready to roll for sample-playback and effects processing.

Analog synthesis and FM synthesis

I contend that the Reface products are a field test for SWP70-based synthesis methods that are not tested by the S970 and S770. I have not yet seen absolute evidence that Reface keyboards use the SWP70, but my suspicion is strong.

The Reface CS and Reface DX demonstrate analog physical modeling and 4-operator FM sound synthesis, probably using the SWP70. Please remember that the SWP70 is not just sample-playback; there are digital signal processors in there. These DSP units can be programmed for effects (reverb, etc.) or sound generation. A computer is a computer whether it is an x86 architecture machine or an embedded DSP. Both the Reface CS and Reface DX implement VCM effects, too.

Two more general points about the Reface line. First, the Reface keyboards use an ARM architecture (FM3) processor for control and user interface. This is a major departure from past Yamaha practice. Next, all four keyboards operate on battery power (six “AA” batteries). Low power operation is a significant engineering accomplishment and means that the SWP70 could be deployed in a wide range of portable products — not true of the previous generation SWP51L tone generator.

Acoustic and electric piano emulation

Yamaha demonstrated its commitment to the stage when it introduced the CP1 stage piano and its siblings. The CP1 was well-received.

The CP1 is a bit of a breakthrough product technically. The acoustic piano is implemented mainly through sample-playback. The CP1 physical wave memory is only 128 MBytes. Yamaha eventually released the CP1 acoustic piano samples for Motif XF as part of the Motif XF Premium Collection. We should expect a CP1-level piano or better in the new workstation.

Yamaha “got away” with so few samples overall because the CP1 electric pianos are implemented using Spectral Component Modeling (SCM). “SCM” covers a family of technologies including spectral modeling synthesis (SMS). SMS replaces gobs of samples with computation (AKA “modeling”). SMS eliminates the nasty sonic artifacts due to velocity switched sample-playback because, well, there aren’t any samples, just lots of computations to be performed very quickly.

The Reface CP uses SCM to implement its electric pianos. The Reface CP sounds great. (See my Reface CP snap review.) The Reface CP re-introduces Formulated Digital Sound Processing (FDSP) to model the electric piano pickup. I expect to see SCM electric pianos and a subset of FDSP in the new workstation.

B3 and combo organ emulation

B3 emulation has never been Motif’s strong suit. Nord, in particular, excel at B3 and rotary speaker emulation. Hopefully, Yamaha have addressed this defficiency by incorporating the Reface YC technology into their new workstation.

The Reface YC provides a live front panel that lets a player control the B3 drawbars, percussion, vibrato and rotary speaker on the fly. The ability to play the bars, etc. is essential to B3 technique. A few important improvements include a rotary speaker brake (STOP) position as well as SLOW and FAST, a vibrato/chorus section, and a full percussion section. Hopefully, the vibrato/chorus section emulates the Hammond vibrato/chorus scanner — an effect that is lacking in the Motif (and Tyros/PSR, for that matter).

The Reface YC implements B3 tonewheels through AWM. Is sample-playback better than Nord’s modeling? Of course, a lot rides on rotary speaker simulation, too. I can’t wait to find out. So far, I haven’t been able to find a Reface YC to try one out! If Yamaha wants to take the stage, again, it needs to nail this one.

The bottom line

Yamaha surely have the basic technology to make a machine for stage performers. Hopefully, they have implemented a user interface that is easy to learn, responsive and fun to play — kind of like the live front panels in the Reface series.

The Tyros and the new S770/S970 arrangers sport large displays. The S770 and S970 wide-screens are really nice. Lately, Yamaha have placed greater emphasis on skeuomorphic user interfaces with virtual knobs, sliders, etc. Whether Yamaha goes for a touch panel, only Yamaha knows at this point. It would be kind of cool to have virtual Reface front panels with finger-tweaking controls. But, would it be playable?

Sixteen days to go to Winter NAMM 2016 …

If you liked this article, you might enjoy:

New Yamaha workstation at NAMM 2016?
Reface YC and DX teardowns
The SWP70 tone generator
PSR-S770 and S970 internal architecture
Reface CP: Yes, I played one!

Copyright (c) 2016 Paul J. Drongowski

Reface YC and DX teardowns

Markus Fuller posted two Yamaha Reface teardowns (YC and DX) to Youtube:

In case you’re not familiar with the term “teardown,” think of a teardown as a casual tour through the insides of a keyboard.

Both Reface keyboards have an ARM FM3 handing the user interface panel. The switch to ARM is major news. In the past, Yamaha used Renesas H8 or SH4 microcontrollers for interface applications. They apparently have decided to ride the embedded cost curve and that curve leads to ARM, the current leader in low-power, high function embedded microcontrollers.

I wonder if Yamaha will adopt ARM in their entry-level keyboards? This would be a smart move. Yamaha currently use their own SWL01 processor in battery-powered entry-level products. Now that Yamaha have sold off their integrated circuit fabrication plant, they are free to move to off-the-shelf parts when it makes sense. ARM is the choice for battery-powered embedded devices. Further, the ARM-resident, XG-capable sound engine in Yamaha Mobile Music Sequencer has a better spec than the entry-level ‘boards. (MMS reference)

Both Reface keyboards have a large metal plate over one or more integrated circuits. This is the honey pot. 🙂 I understand Markus’s reluctance to remove the heat sink. This is, however, where the digital signal processing (DSP) is being performed. Apparently, Yamaha had a minor power dissipation problem and resolved it using a simple heat sink (no fan). Heat is an important product design problem; x86 fans take note. (More on x86 and instrument design.)

Here are some notes about the integrated circuits in the Reface YC:

Winbond W9864G6KH-6 SDRAM  (64Mbits)
    4Mx16 bits = 1M words x 4 banks x 16 bits (8MBytes equivalent)
    166MHz/CL3
    Parallel interface
    Burst-oriented accesses

Winbond W9812G6JH-6 SDRAM (128Mbits)
    8Mx16 bits = 2M words x 4 banks x 16 bits (16MBytes equivalent)
    Parallel interface
    166MHz/CL3
    Burst-oriented accesses

AKM AK4396VF (Asahi Kasei Microdevices Corporation)
    Digital-to-analog converter (DAC)
    24-bit 192KHz 128x oversampling
    I2S data interface
    Integrated digital filter

Texas Instruments / Burr Brown PCM1803A
    Stereo analog-to-digital converter
    24-bit, 64x or 128x oversampling
    I2S data interface

The circuits are all pretty typical for a Yamaha design. Not enough information here to indicate whether the SWP70 tone generator is in use or not. Yamaha have used W9864G6KH as DSP SDRAM in past designs.

I’m glad that Markus posts his teardowns. I like it when he zooms in and identifies the integrated circuits. One very small quibble with the YC teardown — I believe the “A” stands for “Acetone.”

While you’re here, catch my Reface CP snap review.